Printing apparatus



EARCH ROGM G. P. TAILLIE PRINTING APPARATUS 2 Sheets-Sheet 1 Filed Sept.

A AA A A A AA INVENTOR. GORDON P.

d'AlLLIE 5 ATTORNEYS July 11, 1967 c. P. TAILLIE 3,330,190

PRINTING APPARATUS Filed Sept. 1964 2 Sheets-Sheet J INVENTOR.

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ATTORNE Y5 United States Patent York Filed Sept. 1, 1964, Ser. No.393,698 1 Claim. (Cl. 954.5)

This invention relates to communication printers and particularly, toprinters of the type wherein a photosensitive surface is exposed, in aline by line progression, to light images of alphanumerical characters.More particularly, the invention is concerned with apparatus forconveying selectively illuminated light images of alphanumericalcharacters from an array of characters to aphotosensitive surface sothat the character appears at the photosensitive surface in an in-linearrangement.

Communication printers receive an electrical signal input which must beconverted to alphanumerical characters and printed on copy paper. Thepresent invention is intended for use in a printer which translatesincoming electrical signals into light images of characters byilluminating areas of a plate containing a series of vertical columnswith each of'the various characters to be reproduced and bringing theparticular characters illuminated into on-line orientation to therebyexpose a photosensitive surface a line at a time.

A device for bringing. optical images into on-line orientation isdisclosed in Patent No. 2,725,786, entitled, Optical Card ReadingApparatus, and a printer of the type suitable for use with the presentinvention is disclosed in copending application Ser. No. 393,699,entitled, Communication Printer, filed Sept. 1, 1964. The devicedisclosed in Patent No. 2,725,786 visually displays characterscorresponding to the punched holes in a data processing card, in astraight line, for ease of reading. The communication printer disclosedin Patent No. 3,149,201 selectively illuminates and prints characters inresponse to electrical signals. The printer includes a cathode ray tubeto illuminate the desired characters and a xerographic reproducing unitto convert the light images into printed copy.

The present invention is an improvement in the means for conveying lightimages to the photoconductive surface of the xerographic unit. Theconveying means shown in copending application No. 393,699, filed Sept.1, 1964, consists of a pair-of mirrors or a glass block which reflectthe light images through a light path from the image source to thephotoconductive surface. Though very effective for thepurpo'se intended,the mirrors or glass blocks tend to be long and space consuming. The

present invention reduces the size of the glass blocks by reflecting thelight through a tortuous path internally and maintaining the length ofthe light the same as if the image were directly focused on an imageplane.

It is the primary object of this invention to improve communicationprinters by reducing the size of the light conveying block used toconvey light images of oil-center characters to on-line orientation at aphotosensitive surface;

It is a further object of this invention to reduce the space used in acommunications printer for the optical path by folding and overlappingthe light path of characters being reproduced.

It is also an object of this invention to improve the optical system ofa communications printer by internally reflecting the light image of thecharacters to be reproduced within a glass block shaped to fold thelight path of the images and to maintain the light path a length equalto the light path necessary to focus the image on a plane coincidentwith the drum surface.

These and other objects of the invention are attained ice by means of aglass plate positioned between the projection lens and the xerographicdrum to receive light images for internal reflection. Some edges of theplate are silvered to reflect the light image through a path, inside theplate, to the xerographic drum.

For a better understanding of the invention as well as other objects andfurther features thereof, reference is had to the following detaileddescription of the invention to be read in connection with theaccompanying drawings wherein:

FIG. 1 is a schematic view of a communication printer suitable for usewith the present invention;

FIG. 2 is a perspective of one embodiment of the light conveying elementconstituting the present invention;

FIG. 3 is a front fragmentary view of a portion of the character plateused in the device shown in FIG. 1;

FIG. 4 is a schematic illustration of the spatial orientation ofconventional projection optics;

FIGS. 5 and 6 are alternative embodiments of the light conveyingelement.

FIGURE 1 shows a schematic representation of one embodiment of acommunication printer. The printer con- 'tains a xerographic drum 10having a photoconductive surface thereon; a flying spot cathode ray tube12; a relay lens 13 in front of the cathode ray tube; a field lens 15 infront of an opaque plate 14, containing an array of transparentalphanumerical characters, positioned in front of the relay lens 13 andthe cathode ray tube 12; a projection lens 18; a character positioningelement 16, in the form of a glass plate, adapted to convey light imagesfrom the lens 18 to the xerographic drum 10; and an input logic I 20,operatively connected to the cathode ray tube 12 to position the lightspot of the cathode ray tube relative to the matrix on the plate 14 inresponse to an electrical signal.

The apparatus shown herein for translating optical images to printedwords on a sheet of paper is a xerographic apparatus which is well knownin the art. The same results may be accomplished by using anyphotosensitive surface in place of the xerographic drum 10, however, aXerographic apparatus has been shown as illustrative of the type thatmay be used. The drum 10 containing a photoconductive surface, which isnormally an insulating surface in the dark, is driven through a seriesof process stations by a motor MOT-1. The motor MOT- 1 is adapted toadvance the drum a line at a time. That is, after exposure of one lineon the drum surface the drum is advanccdone line by the motor MOT-1. Thedrum is stopped as each line is printed so that thecharacters appear onthe drum surface in a straight line. This permits variable character andline printing time. It is also possible to skew the glass plate relativeto the drum axis so that a line may be exposed with the drum movingWithout producing distortion of the line.

As the drum 10 is driven by the motor MOT-1 past a charging station A, aCorotron 22 places a uniform electrostatic charge on the surface of thedrum. The drum then rotates to an exposure station B wherein the drumsurface is exposed to a light image of the characters to be printed. Thelight of the images renders the photoconductive surface conductiverather than insulating and discharges-the electrostatic charge in theimage areas so that the drum surface contains uncharged areas in imageconfiguration. The drum then rotates to developing station C wherein adeveloper material containing a triboelectric charge of the samepolarity as the charge on the drum surface is cascaded over the surfaceof the drum. The developer material consists of a finely divided,pigmented, resinous powder herein referred to as toner carried on thesurface of glass beads herein referred to as carrier. particles. Thedeveloper material is supplied from a reservoir in the bottom of thedeveloper housing 24 to the '1 .J plate surface by means of a conveyor26 and is cascaded over the drum surface back to the reservoir at thebottom of the developer housing. The carrier particles carry the tonermaterial from the reservoir to the drum surface and upon contact withthe non-charged image areas the toner material adheres to the drumsurface, while in the non-image or charged areas the toner material isrepelled by the charge onthe drum surface and returns with the carriermaterial to the reservoir. Thus, a powder image of the light image towhich the drum was exposed at station B is developed on the drumsurface. The drum then rotates past a transfer station D wherein a webof paper or other suitable material 28 is supplied from a supply roll 30over a pair of guide rollers 32 into contact with the surface of thexerographic drum. A transfer Corotron 34 places an electrostatic chargeon the surface of the web of paper while the paper is in contact withthe drum surface. The electrostatic charge is of opposite polarity tothe charge on the toner material and thus attracts the toner materialfrom the surface of the drum onto the Web of paper. The paper thenpasses through a heat fuser 35 wherein heat supplied to the paper andthe toner material causes the toner to coalesce and bond to the surfaceof the web. The web then contains a permanent image of the powder imagetransferred from the drum surface to the paper and is accumulated on atakeup roll 36. After the transfer operation the drum is rotated past acleaning station E wherein a pair of rotating brushes 38 remove anyresidual powder from the drum surface prior to recharging andre-exposing the drum. The operation of a xcrographic apparatus is wellknown in the art and does not require a detailed discussion herein.

FIGURE 2 illustrates a system whereby a cathode ray tube provides a highintensity light spot behind selective characters on a plate. The plate14 is constructed of opaque material with an array of transparentcharacters thereon. The character plate 14 may be exposed photographicfilm with unexposed character areas, or any other suitable material thatwill give high character resolution. The plate contains vertical columnshaving all the character symbols required of the printer and contains asmany identical columns as are required to form a printed line across thewidth of the copy being printed. A segment of the character plate 14 isshown in FIG. 3.

As shown herein, the plate 14 is mounted adjacent to the exterior faceof the cathode ray tube with a relay lens interposed to focus the lightspot on the plate. However,

the plate may be mounted internally in the tube on the.

phosphor surface. Also, when the plate is mounted outside the tube it issometimes advantageous to eliminate overlap of the light spot on morethan one character by conveying the light from the phosphor surface tothe particular spot desired by fiber optic bundles running from insidethe tube face to the characters.

The projection lens 18 normally would reproduce the spatial orientationof each illuminated character at a focal plane tangent to the drum andperpendicular to the optical projection axis, as shown in FIG. 4.Element 16, shown in FIG. 2, is a glass plate which serves to interceptthe light leaving the projection lens in such a manner as to opticallydisplace all characters, disposed vertically in the image plane, to theoptical axis while their horizontal positions remain unaffected. Thus acapability is created for a simple optical input with no movingparts andwith a I either transmission lines or computer input after beingtranslated by the input logic 20.

For purposes of illustrating the relationship between the characterplate, the projection lens and the image plane, FIG. 4 shows a schematicrepresentation whereby the characters on the character plate passthrough a projection lens and are focused on an image plane. Forsimplicity the rays of each character are drawn to represent only therays from the center of each character that passes through theprojection lens. In order to focus all the characters from the plateonto the optical axis at the image plane rather than in the spatialorientation shown, the glass plate 16 is placed between the projectionlens and the image plane. The light rays from the characters on theplate then pass through the projection lens and are immediatelyintercepted by the plate 16. Each of the characters is reflected betweenthe surface of plate 16, through a light path equivalent in length tothe original light path from the projection lens to the image plane plusa correction for the index of refraction as the light enters the glassplate. That is the length of the light path within the sheet isdetermined by takingthe light path from the projection lens to the imageplane in air and multiplying it by the index of refraction of the glass.This added length compensates for the changing of the angle of the lightpath as it enters the glass sheet and thus the angle at which the lightrays intercept the surfaces of the glass sheet during reflection towardthe image plane.

The spacing or separation of the reflective surfaces is equal to thevertical center to center distance between the characters in theprojected image plane. The number of reflections of each characterbetween the surfaces is dependent upon its position above or below theoptical axis. It should benoted that the centrally located character inthe column does not experience any reflection between the surfaces whileeach successive character above and below experienced reflections innumber equal to their numerical position from tthe central character.Therefore, in order to have the characters all appear upright at thephotosensitive surface their orientation in the vertical sense must bealternated on the character plate as shown in FIG. 3. The embodiment ofthe invention shown in FIG. 2 reduces the overall size of the printer byreducing the size of the light conveying element or glass plate 16.

The glass plat eprlight conveying element 16 is conso that the lightrays are uniformly reflected regardless of the direction in which theyare traveling. The light rays intercept the top and bottom surfaces ofthe element 16 at an angle less than the critical angle and arerefiected internally along the paths shown in dotted lines in FIGS. 2, 5and 6. The plate 16 is shaped so that the light rays as illustrated bythe dotted lines in FIG. 2 pass through a tortuous path within the glassplate so that thelength of the light path from the lens 18 to thexerographic drum 10 is equal in length to the light path through astraightlight conducting element such as that shown in FIG. 1. The lightrays passing through len sglfi are intercepted by edge 40 of the glassblock and die refiected between the parallel top and bottom surfaces ofthe glass block to the point where they intercept the opposite edge 42.The edge surface 42 is silvered to reflect the light rays back into theglass block along the path illustrated by the dotted lines to a thirdedge surface 44 which is also silvered to reflect the light rays towardsthe xerographic drum 10. The light rays then continue to be reflectedbetween the parallel surfaces of the glass plate until they interceptthe edge 46 which is clear rather than silvered, and'whereat the lightrays leave the glass plate and expose the photosensitive surface of thedrum. As pointed out above the total length of the light path, asindicated by the doted lines, is equivalent to the length of light pathin a straight light conducting element as shown in FIG. 1. The angle ofedge surfaces 42 and 44 are constructed to reflect the light rays alongthe path desired to ultimately reach the xerographic drum.

The plate 16 .is a relatively thin plate and when extendedlongitudinally as illustrated in FIG. 1 the length of the plate is largeand space consuming. The length to thickness ratio is particularly largein the straight longitudinal plate and creates problems in obtaining there quired degree of flatness on the exterior surfaces. By folding theoptical system as shown in FIG. 2 the overall size of the glass plate 16is considerably reduced and the size of the length to thickness ratio isalso reduced. Thus there is a savings in construction of the elementitself and in the overall size and construction of the printer.

Two alternative embodiments are shown in FIGURES I 5 and 6 wherein thelight conducting element 16 has silvered edges at 48 and 50 in FIG. 5and at 52 in FIG. 6.

In operation, a plate of the type shown in FIG; 3, containing a font ofcharacters, arranged in vertical columns containing each of thecharacters to he used in the printing process and horizontal rows ofidentical characters, is placed on the face of the cathods ray tube oradjacent to the tube with a relay lens interposed between the tube andthe plate. A signalis received from a remote source,

such as a communications transmiter or a computer output and, throughthe input logic 20, is used to control the orientation of. the lightspot of the cathode ray tube. lf :1 character is to be printed in agiven position then the spot of the cathode ray tube illuminates acharacter in the corresponding column on the plate in response to theinput signal. The light passing through the plate is focused by theprojection lens and intercepted by the transmitting element 16 andinternally reflected to the photosensitive surface 10. After thephotosensitive surface has been exposed to a full line of print the drumis stepped by one line and the spot in the cathode ray tube'again startsto scan the character plate for the printing of the next line.

While the invention has been describedwith reference to the structuredisclosed herein, it is not confined to the details set forth, and thisapplication is intended to cover such modifications or changes as maycome within the purposes of the improvements or the scope of thefollowing claim.

I claim:

In an optical system for a communication printer of the type wherein aphotosensitive drum surface is exposed in a line by line sequence tolight images from a matrix of transparent characters which areselectively illuminated and placed along a predetermined axis on thedrum surface, the optical system including:

a lens positioned to receive light rays of selected illuminatedcharacters and being capable of imaging the received light rays in aplane perpendicular and tangent to the predetermined axis on thephotosensitive drum,

an optical element having two parallel surfaces joined by a plurality ofspaces, each space being perpendicular to the parallel surfaces suchthat the faces cut the individual planes described by each of theparallel surfaces into irregular polygons having at least four sides,

said optical element having a light my entry face in juxtaposition tosaid lens, said entry face being. perpendicular to the geometricalcenter line of said lens, the parallel surfaces being positioned so theyare equidistant from the geometrical center line of said lens such thatthe imaging light rays directed from said lens are reflectedtherebetwccn for off axis characters,

said optical element having an exist face angularly disposed from saidentry face, the exist face being in a plane parallel to the image planeand positioned adjacent said drum along the predetermined axis thereon,and at. least two other reflecting spaces arranged to redirect theimaging light rays entering said element at the entry face towards theexit face.

References Cited UNITED STATES PATENTS 2,388,961 11/1945 Elliott -452,682,194 6/1954 Roscnburgh 88-24 2,725,786 12/1955 McCarthy 954.5 X I2,887,935 5/1959 Scot 95-4.5 2,946,268 7/1960 Moyroud 9.5-4.5 2,979,0264/1961 Reuter 88-24 3,006,259 10/1961 Blakely 95--4.5

JOHN M. HORAN, Primary Exar'nincr.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,330,190 July 11 1967 Gordon P. Taillie It is hereby certified that errorappears in the above numbered patent requiring correction and that thesaid Letters Patent should read as corrected below.

Column 6, line 12, for "spaces, each space" read faces, each face Signedand sealed this 22nd day of April 1969.

(SEAL) Attest:

EDWARD J. BRENNER Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer

